1. Field of the Invention
The present invention generally relates to a socket connector for mounting an electronic device, such as a central processing unit (CPU) module, to a circuit board, and more particular to a housing of the socket connector and a conductive terminal retained in the housing. A method for making a socket connector by two forming operations is also provided.
2. The Related Arts
Socket connectors for mounting an electronic device, such as a central processing unit (CPU) module, to a circuit board are well known and commonly used in the computer industry. FIG. 1 of the attached drawings shows an example of the socket connectors that is referred to as ZIF (Zero Insertion Force) socket connector. The socket connector, generally designated with reference numeral 10, comprises a housing 12 defining an array of open cells 14 in which conductive terminals 26 (FIG. 2) are received and a cover 16 movably supported on the housing 12. The cover 16 defines through holes 18 corresponding to the cells 14 of the housing 12. The cover 16 carries a CPU module 20 with pin legs 22 of the CPU module 20 extending through the holes 18 of the cover 16 and partially into the cells 14. An actuator 24 drives the cover 16 in such a manner to bring the pin legs 24 of the CPU module 20 into contact with the terminals 26 of the housing 12 thereby forming electrical connection therebetween. Examples of socket connectors of this type are also disclosed in U.S. Pat. Nos. 4,498,725, 5,833,483, 6,059,596, 6,142,810, and 6,159,032.
The housing 12 has a top face 28 and an opposite bottom face 30. The cells 14 defined in the housing 12 can be wide-open on either the top face 28 or the bottom face 30 for receiving the terminal 26 therein, respectively referred to as xe2x80x9ctop-loadingxe2x80x9d and xe2x80x9cbottom-loadingxe2x80x9d. In a top loading structure, the cell defined in the housing 12 has a closed bottom with a slit defined in the closed bottom for the extension of a tail of the terminal. The tails of the terminals in a top loading structure are maintained substantially straight for being soldered to a circuit board with the so-called xe2x80x9cthrough-holexe2x80x9d technique. However, in a bottom loading structure, the tails of the terminals are bent to be substantially normal to the terminal to form a solder pad (such as the portion 32 of the terminal 26 shown in FIG. 2) for carrying solder balls that connect the terminals to a circuit board by means of the so-called xe2x80x9csurface mount technique (SMT)xe2x80x9d. Since a bottom loading structure requires a wide opening of each cell in the bottom of the housing, it is in general difficult to firmly hold the terminal to perform a bending operation. Thus, the solder pad is usually formed before the terminal is loaded into the corresponding cell.
Since SMT provides an efficient way of mounting a socket connector to a circuit board, the SMT type socket connectors are prevailing recently. However, the SMT process requires the solder pads of all the terminals 26 to be substantially flush with each other or in perfect alignment. Forming the solder pads before the terminals 26 are loaded into the cells 14 of the housing 12 leads to troubles in ensuring that the solder pads 32 can be substantially flush with each other. This is because the terminals 26 may be loaded into the cells 14 to difference depth. Thus, a method employing a second forming operation for making the solder pad after the terminal is loaded into the corresponding cell to ensure perfect alignment of the solder pads is desired.
Thus, it is an object of the present invention to provide a socket connector having a housing that allows a second forming operation to be carried out on a terminal retained therein.
Another object of the present invention is to provide a socket connector having a housing firmly retaining a terminal in a cell thereof.
To achieve the above objects, in accordance with the present invention, a socket connector comprises a housing having top and bottom faces. The housing defines an array of cells and each cell has an opening in the top face and a closed bottom with a slit defined in the bottom and exposed to the bottom face of the housing. A bump is formed on the bottom face next to each slit. A conductive terminal made by a first forming operation carried out on a metal plate is received in each cell through the top opening. The terminal has a base section positioned in the cell and a solder pad connected to the base section by a neck portion. The base section, the solder pad and the neck portion are substantially coplanar. The solder pad and the neck portion extend through the slit and beyond the bottom face of the housing. A second forming operation is carried out on the neck portions of all the terminals to bend all the neck portions about the bumps whereby the solder pads are substantially parallel to the bottom face. The neck portions are subject to an over-forming operation so as to have a perfect alignment of the solder pads. The bump provides a spring back clearance for the over-forming operation.